1. Field of the Invention
The present application relates to drilling apparatus for directional drilling in utility installations and, more particularly, to housings for drill string instrumentation such as sonde transmitters and the like.
2. Background Description of the Prior Art
Horizontal Directional Drilling (HDD) is a means of boring horizontally underground to provide utility installations and remediation of utility installations already in place. While most open areas are “open trenched” with various trenching equipment, the HDD boring rigs are used to “drill” a bore path under obstacles such as rivers, roads, railroads, other existing utilities etc.
An HDD drill rig consist basically of a boring machine and a drill string including drill pipe, locating electronics (aka transmitter, sonde or transmitter beacon, typically configured as an instrument assembly for being enclosed or packaged within a tubular housing), and a boring bit attached to the front of the drill string. A bore path is plotted and laid out for the contractors. The drilling crew then drills at an angle into the ground along the bore path until the desired depth is reached. The bore is then leveled out and advanced under the obstacle. During this time the locating electronics instrumentation is installed between the drill bit and the drill pipe for transmitting the drill bit's depth, pitch and clock location (e.g., at 12, 3, 6, or 9 o'clock) to the surface. Once the desired bore length is reached under and past the obstacle, the bit is steered toward the surface. The pilot tool is then removed and a reamer can be used to open the hole to a larger diameter while pulling the drill pipe back. If the pilot hole is the desired size, the tool is removed and the pipe, conduit or “product” is pulled back through the hole. During drilling, the drill pipe is fed into the bore 10 to 15 feet at a time. Attached to the front of the drill pipe just behind the drill bit (or, alternatively, a mud motor) is the instrumentation package such as a sonde housing which houses and protects the sonde (transmitter).
With respect to the instrumentation package, currently there are two types of prior art sonde housing designs on the market. The first type of prior art housing is known as an “end load” sonde housing. The sonde is loaded from one end of the housing and secured therewithin. With no “door” or “lid” access to the sonde this design requires “breaking” the connection between housing and drill stem to obtain access to the sonde within the housing. However, this design allows for a full set of “water ports” to be machined within the wall space surrounding the sonde cavity allowing a large volume of drilling fluids to be pumped through the drill pipe and tool. The volume and pressure capacity of this design allow drillers to drive hydro/mechanical drilling tools in the hole often called “mud motors”
The “end load” design is preferred for its flow capabilities and the security it offers for the electronics in the sonde. Secured inside the end load housing, the sonde is rarely lost during the coarse of boring. However, since the transmitter is powered by batteries, the process of disconnecting the drill string from the housing and removing the sonde can be cumbersome and difficult. This is especially true on shorter, smaller diameter “in & out” bores where the tool usually remains on the drill pipe from bore to bore.
The second type of prior art housing is known as a “side load” housing. It is more popular for use with smaller machines without the large pump capacity for mud motor drilling. These rigs use a variety of bits that drill by rotational force from the drill rig transferred through the drill pipe. The side load design allows easy access to the sonde for maintenance, battery changes and replacement of the sonde. On a side load housing the sonde is installed through an opening in the side of the housing that is long enough for the sonde to be inserted laterally, with its axis parallel to the axis of the sonde housing. The sonde is inserted parallel with the housing and secured in place. A housing door or “lid” is then attached to the housing to cover and protect the transmitter.
The side load feature is a time saving design but reduces the number of water ports that may be provided to direct fluid from one end of the housing to the other. This fluid restriction is the primary reason this housing design is not used with the larger machines.
Another drawback to the side load design is that, on occasion during the drilling process, due to deterioration or extreme rotational torque, the side lids or doors become dislodged from the housing. Once the door is dislodged from a closed position or removed the sonde is completely exposed and typically protrudes from the housing or even falls out of the housing. At that point the sonde is usually irretrievable or damaged beyond repair. The cost associated with this failure is usually the loss of the sonde ($2,000-$5,000) plus the added expense of “tripping” out of the hole, making repairs” and tripping back into the bore.
What is needed is an instrument housing for a drill string that provides full protection for the instrumentation, allows full capacity water ports for use with mud motors, provides for ease of assembly into a drill string, and provides an easily adjusted clocking mechanism for the instrument package, and is low in cost of manufacture.